feat(registry): add model modality metadata to registry definitions

- Added `supportedInputModalities` and `supportedOutputModalities` across model entries in `internal/registry/models/models.json`.
- Filled capability metadata for text/image/audio/video-aware models (mainly Claude/Gemini-family and related provider routes), including Gemini image variants and image-generation models.
- Standardized modality descriptors for multimodal compatibility checks in model routing/validation without changing existing token or generation settings.